A novel OTA architecture exploiting current gain stages to boost bandwidth and slew-rate

A novel architecture and design approach which make it possible to boost the bandwidthand slew-rate performance of operational transconductance amplifiers (OTAs) are proposed andemployed to design a low-power OTA with top-of-class small-signal and large-signal figures of merit(FOMs). The proposed approach makes it possible to enhance the gain, bandwidth and slew-ratefor a given power consumption and capacitive load, achieving more than an order of magnitudebetter performance than a comparable conventional folded cascode amplifier. Current mirrors withgain and a push–pull topology are exploited to achieve symmetrical sinking and sourcing outputcurrents, and hence class-AB behavior. The resulting OTA was implemented using the 130 nmSTMicroelectronics process, with a supply voltage of 1 V and a power consumption of only 1μW.Simulations with a 200 pF load capacitance showed a gain of 92 dB, a unity-gain frequency of141 kHz,and a peak slew-rate of 30 V/ms, with a phase margin of 80◦, and good noise, PSRR and CMRRperformance. The small-signal and large-signal current and power FOMs are the highest reported inthe literature for comparable amplifiers. Extensive parametric and Monte Carlo simulations showthat the OTA is robust against process, supply voltage and temperature (PVT) variations, as well asagainst mismatches.